columbia road/randolph court stream restoration july 2015
TRANSCRIPT
A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
Columbia Road/Randolph CourtStream Restoration
July 6, 2015
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Meeting Outline
• Fairfax County Stormwater Management• Project Existing Conditions• Proposed Stream Restoration• Construction Access• Design Schedule• Questions
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Columbia Road/Randolph Court Stream Restoration
Stormwater Management
Department of Public Works and Environmental Services
Land Development
Services
CapitalFacilities
Solid Waste Stormwater
Stormwater Planning Division
Maintenance and Stormwater
Management Division
Wastewater
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stormwater Infrastructure
• Conveyance System– 1,600 miles pipe and
paved channel– 43,000 structures– 6,800 outfalls
• Management Facilities– 1,540 County Maintained – 3,720 Privately Maintained
• State Regulated Dams
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Service Drivers
In response to The Clean Water Act of 1972
• National Pollutant Discharge Elimination System (NPDES)• Virginia Stormwater Management Program (VSMP) Regulations• Municipal Separate Storm Sewer Permit (MS4)• Total Maximum Daily Loads (TMDLs)
– Chesapeake Bay– Local Streams
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Columbia Road/Randolph Court Stream Restoration
Watershed
Watershed: Cameron Run
Subwatershed:Indian Run
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Columbia Road/Randolph Court Stream Restoration
Existing Conditions- 4717 Columbia Road
120 feet of failing gabion walls
Angled culvert outlet discharging at high velocity eroding gabion wall toe
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Columbia Road/Randolph Court Stream Restoration
Existing Conditions- 4717 Columbia Road
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Columbia Road/Randolph Court Stream Restoration
Existing Conditions - 4713 Randolph Court
100 feet of failing gabion walls
Sanitary sewer adjacent to gabion wall failure
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Columbia Road/Randolph Court Stream Restoration
Existing Conditions - 4713 Randolph Court
Runoff from grass floodplain eroding bank behind gabions
High velocity at stream bend eroding gabion wall toe
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Columbia Road/Randolph Court Stream Restoration
Existing Conditions Along Stream
Bottom sections of gabion wirerusted through and losing stone
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Project Constraints
• Complex project design:– In-stream construction
• Diversion of main tributary around construction site• Stream construction access
– Gabion replacement requires Building Permit• County Land Development Services (LDS) structural review
– Other permit requirements:• US Army Corps of Engineers Permits• Virginia Stormwater Management Program Permit• FEMA “no rise”/”no impact” floodplain study
– Gabion Walls• Currently two failed sections• More gabion wall sections will fail in the future
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Indian Run Stream Restoration
• Stream restoration project proposed upstream of this project, from Indian Run Court to Columbia Road
• Combine Columbia Road/Randolph Court project design with Indian Run stream restoration
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• This project will most likely be a combination of Priority 3 and 4 Restoration Approaches
• Limited by Columbia Road culvert invert
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stream Restoration Structures- Cross Vane
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stream Restoration Structures - Root Wads
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stream Restoration Structures - Boulder Toe
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Stream Restoration - Bank Benches
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Proposed Resource Protection Area (RPA) Plantings
• RPAs - vegetated riparian buffer zone:– Protect water quality– Filter pollutants out of
stormwater runoff– Reduce the volume of
stormwater runoff– Prevent erosion
• Reduce the amount of mowed grass within RPA
• Sanitary sewer easement limits types of vegetation
• Plantings provide great benefits to homeowners
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Temporary Construction Access
• Maximum allowed slope of construction access road is 10%
• Project Site Constraints– Steep slopes
• 4717 Columbia Road = 35%• 4712 Randolph Court = 25%
– Mature trees– Existing driveways
• Two feasible temporary construction access routes
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Columbia Road/Randolph Court Stream Restoration
Temporary Construction Access - Option 1
Grade a temporary ramp from 4717 Columbia Road to project site. Ramp
to be removed and site restored following construction completion.
Construction access with hardwood matting to protect tree
roots from construction equipment.
Access stream with temporary ramp at the low point of gabion
wall
Staging and Storage Area
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Columbia Road/Randolph Court Stream Restoration
Temporary Construction Access - Option 2
Install a temporary construction access from 4705 Columbia Road to project site following existing sanitary sewer
easement. Site to be restored following construction completion.
Construction access with hardwood matting to protect tree
roots and sanitary sewer from construction equipment
Access stream with temporary ramp at the low point of gabion
wall Staging and Storage Area
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Tentative Schedule
• Initiate Design Task Order (1 month)• Conceptual Design (5 months)
– Stakeholders Meeting– County Review
• 95% Design (2 months)• Final Design (1 month)
Design Task OrderJuly 2015
Conceptual DesignAug 2015 - Jan 2016
Final DesignMar - Apr 2016
95% DesignJan - Mar 2016
Additional Information
For additional information, please contact
www.fairfaxcounty.gov/dpwes
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Columbia Road/Randolph Court Stream Restoration
Stormwater Planning Division
Catie Torgersen
703-324-5864